amphibians section 30.2. animal classification animals invertebrates vertebrates sponges cnidarians...
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Animal Classification
Animals
Invertebrates
Vertebrates
SpongesCnidariansWormsMollusksArthropodsEchinoderms
Ectotherms(cold-blooded)
Endotherms(warm-blooded)
FishesAmphibiansReptiles
BirdsMammals
Amphibians
- Order Anura- Order Caudata- Order Apoda
Phylum Chordata
What is an Amphibian?
Class Amphibia – means “double life” Starts life in water and changes on land
Evolutionary advantages over fishes Thin, moist skin Most amphibians have four legs Lungs
What is an Amphibian?
Nearly all amphibians rely on water for reproduction
Undergo external fertilization Water is needed to transport sperm
Ectotherms
Ectotherm – an animal that has a variable body temperature and gets its heat from external sources (can’t regulate their body temperature on their own)
Ectotherms
Amphibians become dormant in regions that are too hot or cold for part of the year Many of them burrow into mud and stay there until
suitable conditions return
Metamorphosis
Tadpoles possess fins, gills, and a two-chambered heart as seen in fish
Tadpoles develop legs, lungs, and a three-chambered heart to become adults
Metamorphosis
Young salamanders resemble adults, and they have gills and usually have a tail fin
Most adult salamanders lack gills and fins Adult salamanders have no lungs and breathe
only through their skin
Walking Requires More Energy The evolution of the three-chambered heart
in amphibians ensured that cells received the proper amount of oxygen
Walking Requires More Energy One chamber receives oxygen-rich blood
from the lungs and skin Another chamber receives oxygen-poor blood
from the body tissues Blood from both chambers then moves to the
third chamber which mixes the two types of blood
Walking Requires More Energy Because of the mixture of blood, the skin is
much more important than the lungs as an organ for gas exchange
Walking Requires More Energy Because the skin of an amphibian must stay
moist to exchange gases, most amphibians are limited to life on the water’s edge or other moist areas
Frogs and Toads
Frogs and toads belong to the order Anura Frogs have long hind legs and smooth, moist
skin Toads have short legs and bumpy, thick, dry
skin
Frogs and Toads
Adult frogs and toads are predators that eat invertebrates, such as insects and worms
Many species of frogs and toads secrete chemicals through their skin as a defense against predators
Frog eating bird
Frogs and Toads
Frogs and toads also have vocal cords Vocal cords – sound-producing bands of tissue in
the throat As air moves over the vocal cords, they
vibrate and cause molecules in the air to vibrate
Frogs and Toads
Tympanic membrane – amplifies sounds frogs and toads make
Throat pouches and tympanic membranes increase the loudness of their calls
Frogs and Toads
Frogs and toads are among the first organisms to be exposed to pollutants in the air, on land, or in the water
Declining numbers of frogs species sometimes indicate the presence of pollutants in the environment
Salamanders
A salamander (order Caudata) has a long, slender body with a neck and tail
Salamanders resemble lizards, but have smooth, moist skin and lack claws
Caecilians
Caecilians (order Apoda) are burrowing amphibians, have no limbs, and have a short (or no) tail
They are tropical animals with small eyes that often are blind
Caecilians
They eat earthworms and other invertebrates found in the soil
All caecilians have internal fertilization
Challenges of Life on Land
Some dangers living on land 1. Temperature of water remain fairly constant
while air temperatures can vary greatly
Challenges of Life on Land
2. Without the support of water, the body was clumsy and heavy
The legs of a salamander are set at right angles to the body. This prevent the belly from dragging on the ground.